Fuse



A. F. DAUM.

FUSE.

APPLICATION FILED 05010, T918.

1,378,329. Patented May' 17, 1921.

BY hi@ ATTORNEY I ALBERT F. DAUM, OF PITTSBURGH, PENNSYLVANIA.

FUSE.

Specification of Letters Patent.

Patented May 17, 1921.

A Application filed December 10, 1918. Serial No. 266,057.

To all whom t 'may concern.'

Be it known that I, ALBERT F. DAUM, a

citizen of the United States, residing at' Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented certain new and useful Improvements in Fuses, of which the following is a specification.

This invention relates to improvements in fuses of the inclosed type, being particu- -larly adaptable for use in connection with such fuses having a renewable or refillable characteristic.

Inclosed fuses, generally in the form of tubular casings carrying terminals at the ends in the form of caps or other metallic elements, with the fusible element connecting such terminals either direct or through connections, universally provide metallic elements of stable material both internally and externally of the insulating casingthe fusible element itself being considered as unstable in the presence of predetermined temperatures. In some forms, the fusible element is secured to the internal stable formation; in other forms the element is clamped or otherwise secured in contact with the stable formation, the general pur pose being to not only secure the element in position but, in addition, to provide an extended heat-dissipating zone at the ends of the casing serviceable to prevent blowing the element adjacent theend, and thereby tending to restrict the point of disruption more or less remote from such ends. This necessitates the use of stable metallic structures as essential elements of the fuse,there by providing a material cost, factor in the manufacture of the fuse. One of the objects of the present invention is to eliminate this cost to a considerable extent by dispensing with these stable structures, thus not only reducing the fuse cost as a whole, but also providing a saving of metallic materials heretofore required in fuse production.

Another characteristic of such prior fuses is that while such zones may tend to restrict the point of disruption to an intermediate point of the casing, this safety factor is present only where no arc is left by the disrupting action, it being readily linderstood that the formation of an arc simply7 acts to maintain the circuit with the heat factor active in the form of the arc, so that disruption continues with an increase in the length of the arc, until the latter reaches the stable structures, bringing about conditions for sustaining the arcbetween these structures. To prevent this action it has been the custom tov pack the casing with a c suitable filler, the purpose being to quench the arc through the presence ofthe filler, thus preventing the arc reaching the stable structures. The use of a filler not only adds to the cost of manufacture, but where the f use is of the renewable type, difficulty or time loss is present when a new 4element `is to be inserted since this packing action must be had with each re-filling operation. Another object of the invention is, therefore to eliminate this difficulty by eliminating the necessity for using a ller and at the same time provide against any formed arc reaching any stable metallic structure. This ob- ]ect is attained by leading the ends of the fusible element to the exterior of the fuse 1n such manner as to produce an efficient barrier between the internal and external p ort1ons of the element, such barrier serving to prevent the arc from reaching the exterior portions. This barrier effect may be produced in different ways based generally on the fact that the direction of lead of the end portions of the element is angularto that of the intermediate portion, so that these end portions emerge through the side of the fuse-either through the casing or the end closure (both of insulating materi'aD-thus interposing the latter in the path of any arc, the latter being required to change its direction and pass through a relatively narrow slot in attempting to fol low the end portions on to the exterior of the fuseconditions conducive to the quenching of the arc. The externalends may be' connected to terminals of stable material, but itis preferred to employ these ends as the terminals by simply carrying them circumferentially of the fuse, in which case the fusible element may form the only metallic portion of the fuse.

The invention is applicable for use with inclosed (non-renewable) or renewable fuses, being of a form which requires no difficult operations in renewing the element.

Another object is to provide a structure of this type which is indicating in operation.

Other objects are to provide a construction which is simple and efficient in operation, durable in construction, and which can be manufactured at low cost.

To these and other ends, the nature of which will be readily understood as the invention is hereinafter disclosed, said invention consists in the improved cconstruction and combination of parts hereinafter fully described, illustrated in the accompanying drawings, and more particularly pointed out in the appended claims.

In the accompanying drawings, in which similar reference characters indlcate similar parts in each of theV views`,+

Figure l is a view, partly 1n'seet1on and partly in elevation, showing varlous ways 1n which the present invention may be carried into effect.

Fig. 2 is a side elevation of a fuse structure illustrating a way in which the end terminals may be located on the fuse.

Fig. 3 is a perspective view of one of the fusible elements in condition for insertion.

Fig. 4 is a perspective view illustrating the manner in which the curled end of the fuse may be treated to position it wlthin the fuse casing.

A preferred form of a non-indicating fuse is illustrated in Fig. 2, this particular form being shown at A in Fig. 1. In this form, 10 indicates a tubular caslng of suitable length and formed of insulating material. 11 indicates one form of end plug or closure which may be employed, the plug havingan external portion 11a and a reduced portlon 11b which enters the end of the casing; the plug is preferably formed of suitable insulating material. The fusible element 1s 1n strip form and indicated at 12.

As shown in Fig. 1 at A, casing 10 may be provided with a slit or kerf 10a extending longitudinallyl from the open end of the casing, the lengt of the slit preferably slightly exceeding the width of the fuslble element. Plug portion 11b is also slitted, as at 11c (forms A and B of Fig. 1) the slits of the plug and casing being alined when assembled.

Assuming both ends of the casing to be of similar formation, the fusible element when in position to complete the fuse, has an 1n termediate portion 128L of a length substantially equalv to the length of the casing, -and two end portions 12b extending transversely of the direction of length of the intermediate portion and extending through slits 10"L to the exterior of the casing and simply laid circumferentially around such exterior, extending but part way around or entirely around as may be desired.

The change in direction of the fusible element may be provided in any suitable manner, a preferred way being to fold the element upon itself at right angles at this point, thus producing a double thickness of generally triangular form at this point. v As this bendis made at a point approximately the end of the casing, it will be understood that this doubled portion is located within slit 11n asis that portion of the strip leading from the bend to slit 10". '.With the element properly positioned and the plugs inserted,

" the latter are preferably secured in position provided at points spaced a greater distance than the length of the casing, to take care of the diiiculty of passing one end of the element through the casing, but such arrangement tends to buckle the intermediate portion 12*3L Where both ends of the casing are slitted, as in Fig. 2. This difficulty is not materially present Where an end plug and element position is had as in form B-presently described, so that the inserted end of the strip will remain unbent until after it has passed through the casing and the opposite end seated.

However, where the form of Fig. 2 is employed, the element may be inserted by following the practice now described. After the bends have been made at the proper points, the end to be inserted is curled or coiled as in Figs. 3 and 4;, thus reducing the end portion to a form which will pass through the casing without affecting the bend. The uncurled end is then placed within the slit 11c of an end plug 11 and the curled end of the fusible element introduced and passed through the casing as in Fig. 4, this actlon bringing the plug portion 11b within the casing, it being understood that as the latter passes to position it will be introduced in such manner that the projecting end portion will pass into slit 10a of the casing, by alining slit l1c with slit 10a. If desired, pin 13 may now be placed in position to locate the plug seated; if the pin passes through the strip, its introduction will provide the opening for the passage of the pin. This secures one end of the fusible element, with the opposite end projecting from the casing in curl form. This curl is then straightened out in such way as to bring its transverse portion through slit 10, after which the remaining end plug may be inserted, positioning its slit 11c in such manner as to receive the positioned end portion of the element, after which the pin 13 is inserted. The projecting ends are then simply placed about thc casing, completing the se, the terminals of which are provided by these external strip portions which are brought into contact with the clip fingers of the fuse support.

From this it will be seen that the intermediate portion of the element-Which may be slotted or kerfed at an intermediate point, if desired, this being a well known practice to locate the point of disruption-extends from one end plug to the other, entering into the slits 11c at the ends, and then continuing transversely through slits l0a to the exterior. Should, therefore, an arc be formed as the element disrupts, the continued destruction of the unstable element under a sustained arc, may continue until it reaches the plug, whereupon it would be required to p ass 1nto the slit l1, longitudinally of .the casing and then transversely through this slit and slit l0L before the arc could reach the stable metallic clip contacts. Obviously the change from the open space of the interior of the casing into the confined slit spaces, together with the fact that the walls of the slits form parts of comparatively large elements normally cool and tending to absorb heat, will prevent the arc from following this course, these parts having the effect of a barrier against the passage of the arc although permitting the free passage of the fusible element itself.

It is necessary only to remove the pins by driving or pushing them out of the casing to permit the plugs to be removed and expose the interior ofthe casing for renewal purposes.

If desired, one or both ends of the fuse may be formed as shown at B, wherein plug portion 11L is of greatly increased thickness, with slit 11c extending into this portion. In this form, the element end portion is brought out through slit 11c and applied externally of the plug instead of the casing, the pin passing through portion 11b as before, either through the strip as shown in form B or by-passing the strip as in form C. Obviously, one end may employ form A, the opposite end employing form B, thus producing a fuse of the combination of forms A and B.

The principles of forms A or B can be employed for indicating purposes. For instance, form E differs from form A in employing elongated slots 10" in the casing in place of the simple openings for pin 13;v

the pin occupies the inner end of the slots when the plug is in normal position. With the opposite end of the fuse of the type of forms A or B, the pressures produced within the casing by disruption are free to be exerted on the plug of form E which is thus moved outwardly within the limits of the length of the slots 10b. As will be understood, the plug is anchored in its inner position by driving the pin through the fusible element within slit 11 for the ends of pin 13. Obviously, the shifted position of the plug will afford visual indication that the fusible element has been disrupted, since the distance between the pins in normal position must have increased to permit one pin to shift longitudinally and this can take place only in the presence of a break in the strip intermediate the pins.

The pressure effects of the gases may be increased by sprin action, if desired-and this is preferredy increasing the length of portion 11b, as in form D, and placlng a coil spring 14 about the projecting portion, utilizing slots l0b in the casing. By forcing the plug inwardly to compress the spring before inserting the pin, and locating-the latter at the inner end of the slot, the engagement of pin and element as the pin passes through the latter, prevents the spring from expanding, thus tending to place the element under tension. When disruption takes place the spring rapidly expands by reason of the fact that the holding meansthe fusible strip-has been disrupted, so that the tension of the spring can become active, pin 13 shifting Within slots l0", this shifting of the plug serving to not only provide the indicating feature, but in addition tending to break down an incipient arc.

As shown in form F, the features of form D can be employed in connection with the type indicated in form B, the plug being set as in form D'.

Obviously, each of the forms shown may be employed in duplicate form at the opposite ends of the casing, or either form may be employed with either of the remaining forms, as may be found desirable or preferable. In any combination thus produced, however, there is found the same general underlying feature of the end portions of the fusible element extending in directions angular to the direction of length of the intermediate portion, and these external end portions are protected by the barrier effect referred to above. In addition, each form has the external portions operative as terminals, and this is true even if these external portions are secured to metallic portions of stable material external of the fuse. And Where pins 13 are of insulating material, the fusible element forms the only Inetallic material present within the outer surface of the fuse; where metallic pins are employed, their particular location relative to the inner ends of slits 11c is such as to practically prevent the arc from reaching them.

As will be seen, the casing and plugs are of simple configuration, readily produced from insulating material and at relatively low cost, and the same is true of pins 13 and springs 14, if employed. And since the I ruption becomes more or less immaterial, since the destruction of/the intermediate portion of the fusible element can be had Without damage-hence there is. no recurement of the use of an arc-quenching ller, although it may be employed if desired..

Obvlously, under present day conditions of a shortage of metal of the type generally utilized in the formation -of the stable metallic structures, the entire elimination of the latter makes possible the productlon of a fuse even under such conditlons.

While I have herein shown and described various ways in which -the general princlples of the present invention may be produced and em loyed, it`will be readily understood that c anges or modifications therein may be foundA essential or desirable to meet the 4exigencies of use or service or preferences of users, and I desire to be understood as reserving the right to make any and all such changes or modications as may be found desirable or necessary, in so far as the-same may fall Within the broad spirit and scope of the invention as expressed in the accompanying claims when broadly construed.

Having thus described my invention, what I claim as new is:

1. An inclosed fuse comprising a tubular casing of insulating material, end closures therefor, and a fusible element of strip form having its end portions exposed externally and circumferentially of the fuse and an intermediate portion traversing the interior of the casing in the direction of casing len h.

2. A refillable fuse comprising a tubular casing of insulating material, removable end closures therefor, and a fusible element of strip form having its end portions exposed externally and circumferentially of the fuse and an intermediate portion traversing the casing in the direction of casing length.

3. An inclosed fuse comprising a tubular casing of insulating material, end closures therefor of insulating material, and a'fusible element of strip -form having its end portions ex osed externall and circumferentially of t e fuse and an lntermediate portion traversing the interior of the casing in the direction of casing length.

4. A reillable fuse comprising a tubular casing of insulating material, removable end closures therefor, and a fusible element of strip form having an intermediate portion traversing the casing in the direction of casing length, saidstrip being b ent to lead its end portions in directions angular to such intermediate portion to locate such portions externally exposed on circumferential portions of the fuse.

5. A fuse of the type disclosed in claim 4 characterized in that the bends are located in unexposed positions.

6. In a refillable fuse, a tubular casing of insulating material and having a slot extending longitudinally of an end of the casin a fusible element extending longitudina ly of the interior of the casing and having an end portion projecting through /said slot and externally exposed on the outer face of the casing, and means for closing the end of the casino'.

7. In a rellable fuse, a tubular casing of insulating material and having a slit extending longitudinally of an end of the casing, a fusible element extending longitudinally of the interior of the' casing and having an end portion projecting through said slit and externally exposed on the outer face of the casing with the exposed end positioned to form a terminal and a removable plug closing the end of the casin 8. A refillable fuse of the inclosed type comprising a tubular casing having a removable end closure, and a fusible element of strip form having an intermediate portion of its length 'Within the casing and operative as a line protecting structure and an end portion Aextending through the casing and positioned to provide an exposed contact on the cylindrical surface of the casing.

9. A refillable fuse of the inclosed type comprising a tubular casing having a removable end closure of insulating material, and a fusible element of strip form having an intermediate portion of its length Within the casing and operative as a line protecting structure and an end portion extending 100 through the casing and positioned to provide an exposed Contact on the cylindrical surface of the casing.

10. A reillable fuse of the inclosed type comprising a tubular casing having a re- 105 movable end closure, and a fusible element of strip form `having a portion operative internally of the casing as a line protecting structure and externally of the casingin the form of a fuse terminal with the terminal f positioned on the cylindrical surface of the casing.

11. A fuse of the type disclosed in claim 7 characterized in that the plug is slitted to receive a crtion of the fusible element.

12. A.' use of the type disclosed in claim 1, characterized in that the end closures extend within the casing and are slitted to receive portions of the fusible element.

13. A refillable fuse comprising a tubular casing, a slitted removable plug closing an end thereof, and a fusible element of strip form extending internally of the casing and externally of the casing With an intermediate portion extending into the plug slit, said external portion being positioned to form a terminal, said plug being movable in the direction of length of the casing in the presence of element disruption therein to serve to indicate the blo-Wn condition of the fuse.l

extending into the plug, and securing meansl carried by the plug and extending into a casing slot.

15. A refillable fuse comprising'a tubular casing having a longitudinal slot, a slitted removable plug closing an end of the casing, a fusible element of strip form extending internally of the casing and externally of the casing with an intermediate portion extending into the plug slit, means for securing the strip at the opposite end of the easing, a spring interposed between 'the plug and the casing end, and means extending into said casing slot and the plug and extending through the strip portion therein, to; normally maintain the spring under tension, whereby disruption of the element within the casing will release the spring tension.

16. As a means for preventingmaintenance of an *are in fuses of the inclo'sed type, a tubular yeasing of insulating' material closed at its ends to form an inelosed chamhaving a fusible element ber, said casin chamber and projecting traversing sai laterally therefrom to provide line connec-v tion with the element externally of `the casing when the fuse is positioned for active service and locate the chamber walls as an arc-disrupting formation intermediate the chamber and a stable conductor.

17. As a means forv preventing maintenance of an arein'fuses of the inclosed type, a. closed tubular casin of insulating materlal having a fusible element traversing the interior of the casing and projecting through the casing walls to provide a line connection with the element externally of the casing when the fuse is positionedfo-r active serv- K ice and locate the latter as an arc-disrupting structure between the interior of the casing and a stable conductor.

18. As a means for preventing maintenance of an arc in fuses of the inclosed type, a tubular casing of insulating material, a plug of insulating material closing an end thereof, and a fusible element of strip form extending internally of the casing and externally of the fuse with an intermediate portlon extending into the plug, said'plug having a formation to prevent arc-maintenance with respect to the strip portion within the plug, whereby a sustained arc is prevented from reaching the external portion of the stgip.

19. A refillable fuse ofthe inclosed type Comprising a tubular Casin having an end closure slitted longitudinal and a fusible element of strip form having an 'intermediate portion of its length within the casing and operative as a line protecting structure and an end portion extending into theplug slit and outwardly therefrom laterally and positioned to provide an exposed contact on the peripheral surface of the closure.

ALBERT F. DAUM. 

